The 7-step approach to managing otitis (Proceedings)

My goal is to provide you with a set of questions to guide you through the pitfalls and obstacles associated with diagnosing, treating and successfully managing canine and feline otitis cases. Let's get started!

Is this a case that should be managed medically or surgically?

Gentle manipulation of the pinnae and the annular cartilage will allow you to make this determination. If the tissue is fibrous and completely non-flexible it is highly unlikely that medical management will resolve this condition. The only intervention that will "dissolve" or remove calcified ear cartilages is surgical in nature. That being said, not all patients should have bilateral TECA-BO at birth, despite their breed predilection for chronic and severe ear disease. We see many cocker spaniels and poodles that do not have any evidence of otitis. In addition, dogs with first-time cases of otitis are not likely to require surgical treatment unless neoplasia or a foreign body is contributing to the condition.

What is the neurologic status of the patient? Additional methods to assess integrity of the ear cartilages as well as condition of the tympanic cavity and related structures include radiographs, CT scans and magnetic resonance imaging. Advanced imaging techniques provide additional diagnostic information as well as prognostic information for outcome, especially if there is uncertainty regarding need for surgery.

Is the otitis unilateral or bilateral in presentation? What is the age of presentation?

A unilateral case of otitis is unusual and prompts further investigation into potential underlying causes.

     √ If the patient is young: consider a foreign body, hypothyroidism, CARF (cutaneous adverse reaction to food)

     √ If the patient is older: in addition, consider neoplasia sooner rather than later!

Atopic dermatitis can also present as a unilateral otitis, however the age of onset (1-6 years of age, typically) and additional clinical signs, such as a seasonal component, are expected. Hyperadrenocorticism can also contribute to otitis, especially if calcinosis cutis lesions form in the soft tissues near the tragus, causing significant inflammation and pruritus.

Bilateral cases of otitis are much more common and typical of allergic disease and thus the importance of clinical recognition is most helpful when looking for primary causes for these disorders. Autoimmune skin disease can also contribute to the development of otitis, however the pinnae is almost exclusively involved. Upon otic examination, the ear canals of patients with diseases belonging to the pemphigus complex or lupus classification are usually normal.

Are there any symptoms to support an underlying disease process?

A complete and thorough history is essential in order to identify any potential underlying disease process as a cause for otitis, especially recurrent cases. Getting this information takes time, however, thus focusing on a few key questions will allow the clinician to get good information without having to ask a myriad of questions. More challenging cases will, of course, require more extensive history taking. Essentially we are attempting to determine whether an underlying disease process exists, and if so, is the patient suffering from an allergic disorder or an endocrinopathy? In doing so, the most important questions to ask are:

     • Is the patient pruritic anywhere else—face, feet, perineum?

          o If so, the clinician must treat and resolve any secondary infections.

     • When secondary infections have been treated and resolved (including the yeast or bacterial otitis), is the patient still pruritic?

          o If so, consider allergic disorders.

          o If not, consider endocrinopathies.

          o If the patient is pruritic, are the symptoms seasonal or non-seasonal?

               • If seasonal, consider atopic dermatitis.

               • If non-seasonal consider adverse reaction to food or non-seasonal atopic dermatitis

     • Age of onset:

          o Less than 1 year of age with non-seasonal pruritus = rule out cutaneous adverse reaction to food.

          o Older patient with non-seasonal pruritus = rule out cutaneous adverse reaction to food (don't forget about neoplasia in elderly patients!).

          o Between 1-3 years of age (up to age 6) = if symptoms are seasonal, consider atopic dermatitis. If non-seasonal, rule out cutaneous adverse reaction to food.

     • Do the symptoms completely resolve with steroid administration?

          o If so, consider atopic dermatitis.

          o If not, consider cutaneous adverse reaction to food, especially if the symptoms are non-seasonal in nature. **Don't forget to treat and resolve secondary infections....

What are the complicating factors present within the ear canals that will affect my treatment choices?

The ability to successfully treat and resolve otitis cases depends upon the ability to get the selected medication to its intended target site. Changes within the ear canal that are important to document and consider during otoscopic evaluation include:

     • Inflammation

          o Is the erythema mild, moderate or severe? Is the epithelium friable? Does it bleed easily? Are ulcers present?

     • Cerumen gland hyperplasia

          o Mild, moderate or severe? Are they occluding the canals?

     • Stenosis

          o Is this a breed with naturally stenotic canals? Is the stenosis due to edema or hyperplastic cerumen glands?

     • Characteristics of exudate

          o Is the exudate purulent? Is it waxy, dry, or adherent to the walls of the canals?

     • Status of tympanic membrane

          o Is the membrane visible? If so, is it normal in appearance or thickened and opaque? If a bulging structure is present, is it the pars flaccida? Is otitis media complicating resolution of this infection?

          o *Initially the tympanic membrane may not be visible until the recheck appointment because of the degree of exudate and inflammation present within the ear canals.

Cytology findings should always be utilized in combination with the above observations when choosing an appropriate therapy.

The most commonly encountered pathogens of the ear are:

     • Malassezia pachydermatis

          o Yeast organisms noted on cytology. Rarely, inflammatory cells are noted. Commonly, budding yeast organisms are adhered to keratinocytes and are found in clumps.

          o The exudate is frequently waxy and/or dry and dark brown in color.

          o An intense inflammatory response is often noted – intense erythema and pruritus.

          o Most infections can be resolved with topical clotrimazole or miconazole containing otic preparations.

          o A topical steroid is also recommended to reduce the intense inflammatory response, normalize the size of the cerumen glands (thus decreasing cerumen production) and improve patient comfort.

          o Fourteen (14) days of therapy is usually sufficient.

          o Combine with a cerumenolytic (if excess cerumen is present) and acidifying ear cleaner used twice weekly.

     • Staphylococcus pseudintermedius

          o Cocci noted on cytology.

          o The exudate is of variable consistency and clinical findings are variable.

          o Most isolates are readily eliminated with standard topical antimicrobial preparations containing neomycin or gentamicin.

          o Fourteen (14) days of therapy is usually sufficient.

          o Combine with a ceruminolytic (if excess cerumen is present) ear cleaner used twice weekly. If the ear is painful or ulcerated a neutral pH cleaner is preferred to minimize inflammation due to use of acidic products.

     • Pseudomonas aeruginosa

          o Rods or a mixed infection noted on cytology. **Culture and susceptibility testing is indicated. **

          o Inflammatory cells (neutrophils) may be seen on cytology.

          o Intense inflammation, pain, ulceration is expected.

          o Abundant purulent "soupy" exudate is typical.

          o Best managed with aggressive topical therapy.

          o NOTE: Culture and susceptibility testing is performed in order to prove that the infection is caused by Pseudomonas spp. and to evaluate the resistance pattern. It is NOT used to choose an oral antibiotic for treatment. Topical therapy is frequently very effective despite indication of resistance (based on serum levels) by the susceptibility report.

          o Suspect the organism so the infection can be treated aggressively initially. An alternative is to treat with topical/oral steroids while waiting for the initial culture results. Don't select for resistance and make your job more difficult!

Strategies for treating Pseudomonas otitis:

     • An aminoglycoside antibiotic will be inactivated in the presence of large amounts of pus.

     • Always utilize a chelating agent (tris-EDTA) to prevent development of resistance and to remove the abundant purulent exudate.

     • Volume is crucial when treating these cases - the ear canal must be filled with solution, especially when utilizing a tris-EDTA product.

     • Compounded products are often very successful, used wisely.

          o Ticarcillin: an alternative treatment - It's use should be reserved for fluoroquinolone (FQ) failures. Topical therapy instructions: 3.1 gram vial is diluted using 100ml of sterile saline and 1.0 ml aliquots are drawn into 3.0 ml syringes (plus 1 extra ml of air), capped and frozen. The product is stable for 1 month if frozen. Owners are instructed to thaw 2 syringes each am and pm, allowing the syringes to reach room temperature, and the solution is then infused into the external ear canals, which are then massaged for 30-60 seconds.

               • 1 vial (100 syringes) will last for 25 days in a dog with bilateral disease.

               • **Malassezia overgrowth is commonly noted following treatment with Ticarcillin and will require treatment with an appropriate antifungal otic.

          o High dose topical enrofloxacin: Targeting 20 mg/ml this suspension utilizes the large animal formulation of enrofloxacin (100 mg/ml). Mixed with a chelating agent (tris-EDTA) it is very successful when treating Pseudomaonas spp. infections that have not yet acquired an efflux pump mediated mechanism of resistance. Once an efflux pump population is established this therapy is no longer effective and the cellular target must be altered.

          o Polymyxin B: Also effective against Pseudomonas spp. but can be ototoxic. It's cost is frequently prohibitive. It's activity is also inhibited by cellular material.

          o Silver sulfadiazine: 1 part cream to 9 parts water for use as a suspension. Messy and difficult for owners to use. We do not utilize this in our clinical practice.

What compliance obstacles should be anticipated?

With painful ears it is often difficult for owners to apply topical medications. Many owners wish for "the magic pill" which also does not exist in most cases. Knowing this prior to designing a therapeutic plan for each client - patient is crucial for success. If pain is preventing the owner from medicating the ears, consider oral steroids rather than topical preparations for a few days to decrease the swelling and pain associated with administering topical medications, delaying topical therapy until the patient is noticeably more comfortable. Also, try to utilize the fewest number of topicals as possible and choose products that can be administered in measured dose syringes rather than a predetermined number of drops which takes longer for the owner to count and apply to the patient's ears. We all know it is much easier to quickly "squirt" 0.5 ml of a product into a wriggly dog's ear versus counting 8 drops while trying to see how much is applied. When products are difficult for the owner to get into the ears it is very likely that a less than optimal amount of medication is reaching the target site.

Lifestyle considerations are also something to take into account when designing a therapeutic plan. When dealing with organisms that are likely to develop resistance, namely Pseudomonas spp., it is important to utilize chelating agents (i.e. tris-EDTA) in addition to enrofloxacin to minimize resistance as stated above. If these products are administered separately as a "flush" and an "ear drop" it is likely the owner will quickly abandon the "flush" portion of the regimen or the "flush" treatment will occur less often than necessary, especially in a hectic household. For this reason we are frequently looking for "one-stop" treatments that will improve our chances of success.

Aggressive or very difficult to treat patients may require alternative or creative approaches. The use of ear wicks to deliver continual prolonged delivery of medications is an option in some situations. We are currently in the process of evaluating these as treatment options.

What is the long-term goal of the clinician? Of the owner?

At times the desired outcome for the case may vary between the clinician and the owner. Most clinicians desire for the patient to be comfortable at a minimum and we all like to discover the reason for the problem in the first place. In chronic conditions this is not always possible but if we can make a difference in the quality of life of a patient it is always a good feeling. Owners may, on the other hand, expect to treat the condition once and then never want to deal with it again. In this situation they are often asking about surgical intervention. In a patient with allergic disease as the primary problem, however, inflammation, pruritus and lichenification of the remaining ear tissue will continue despite removal of the ear canals with a TECA-BO procedure.

What options are available to manage recurrences?

Patients with allergic skin disease, due to atopic dermatitis or food allergy, those with uncontrolled or undiagnosed endocrinopathies as well as those with keratinization abnormalities are expected to have recurrences of their otitis from time to time. Even those patients well managed with allergen-specific immunotherapy will typically require periodic administration of otic medications, however the episodes of otitis should be less frequent and less severe in nature. Expecting these flares and intervening sooner rather than later will avoid some of the chronic changes that eventually render the ears beyond medical therapy. For these episodes, some products are more desirable than others for periodic administration.

Steroids

Those products containing hydrocortisone are very desirable for management of cases of true allergic otitis (pruritic only without evidence of infection). The more potent steroid formulations are available in either solutions (SynOtic® ) or ointments. When used judiciously this is preferred in most patients to chronic administration of oral or injectable steroids. Each patient is unique and tolerance of steroid treatments varies.

Antifungals + steroids

In addition to the benefits of topical steroids in some patients, the addition of a topical antifungal agent can prevent intense pruritus and inflammation associated with Malassezia otitis. Many allergic patients are prone to overgrowth of both yeast and bacterial organisms because of the favorable environment within the ear canals (as well as other skin fold areas) as a result of the combination of altered keratinization, vasodilation, increase in sebum production and increase in skin temperature. Since these changes occur in conjunction with a flare of allergic skin disease, it is logical that a secondary infection will follow and require therapy. Resistance has not yet been a clinical problem in our veterinary patients thus we often use the steroid component to control and manage more severe cases of inflammation and the antifungal component to treat and resolve any yeast "overgrowth".

Antibiotics + steroids

Most products contain an antifungal agent, an antibiotic as well as a steroid, thus there are few products that contain just an antibiotic and a steroid. Recipes for compounded products are available, however caution should be exercised when using topical antibiotic products prophylactically in ears. With the advent of antimicrobial resistance this practice is not commonly utilized as a preventative measure.

Astringents

These products often contain aluminum acetate (burrow's solution) and come with and without hydrocortisone. Do not combine these products with topical fluoroquinolones due to the reduced efficacy of fluoroquinolones in the presence of cations.

Flushes

Cleaning the ears is an important part of some regimens. Knowing the pH and the ingredients of each product used is important, especially when a patient displays pain or inflammation associated with cleaning. Overly enthusiastic ear cleaning can cause problems as well. Cleaners can be divided into categories based upon their functions.